Beaver dams transform landscapes, turning stretches of flowing streams into still ponds and flooding forests. Now, researchers have found the dams are transformative in more ways than one. Scientists in Sweden have shown that beaver ponds can cause levels of methylmercury—a particularly toxic form of mercury—to rise in downstream waters by as much as 3.5 times the background levels during summer months. Although mercury, a neurotoxin, occurs naturally in the environment, it is also released into the atmosphere when humans burn coal and other fossil fuels. Once it finds its way back to land or water, bacteria in the soil can convert it into its more toxic cousin, methylmercury. As the researchers reported online last month in Environmental Science & Technology, this kind of bacteria thrives in the waterlogged sediments, rich with decaying vegetation, that pile up behind beaver dams. But the increase in methylmercury appears to be temporary. Surprisingly, it doesn’t occur when beavers move back into old dams: Methylmercury levels above and below recolonized dams were nearly identical in the study. This could mean the submerged vegetation that was feeding the bacteria finally rotted away, leaving them with less food, scientists say. They add that their findings support the practice of leaving old dams in place in Europe and North America where beavers—whose numbers have plummeted over the last 150 years—are making a comeback. Next, the researchers hope to figure out how methylmercury works its way through the ecosystem and whether or not it’s accumulating in fish and other organisms.

American Journal of Electromagnetics and Applications (AJEA) provides a forum for sharing timely and up-to-date publication of scientific research and review articles. The journal publishes original full-length research papers in all areas related to electromagnetics and its applications. It aims to contribute to intersciences coupling applied electromagnetics, mechanics and materials. The following categories are accepted: Original researches, case reports, reviews, technology papers and brief communications.

American Journal of Electromagnetics and Applications is a peer-reviewed, open access, online journal, publishing original research, reports, reviews and commentaries on all areas of electromagnetics. Subject areas may include, but are not limited to the following fields:

Good vibrations indeed. Female red mason bees (Osmia bicornis, seen in video) choose to have sex with a male based on how well he can vibrate his thorax. Initially scientists thought that the females were cuing in on how long the males could keep the vibration going—a testament to fitness and stamina. But along the way, researchers discovered that females from a subspecies native to the United Kingdom preferred U.K. males over German members from the opposite subspecies regardless of who could vibrate the longest. This led scientists to wonder whether information about the bees’ geographic origin and subspecies identity was also conveyed through the vibrations. To be sure, they needed away to control for confounding variables, especially odor. Today in Current Biologyscientists report the development of a novel test that uses a vibrating magnet attached to the bees’ thorax to impose one male’s vibrational pattern onto another male’s body. Before the magnet treatment the least compatible bee pairings were U.K. females and German males. But after scientists recorded the vibrations of U.K. males and duplicated them in the magnet strapped to the Germans, the U.K. females became much more receptive. Like Cyrano de Bergerac feeding Christian lines from underneath Roxane’s balcony, the German males had much better luck when they mimicked the premating communication of another. The scientists point out that, in the wild (where there are no magnetic wingmen), the females’ preference for local males’ vibrations could be an early sign of speciation in the red mason bees: If the females of one subspecies stop mating with the other subspecies entirely, the two lineages may eventually become incompatible and diverge into two separate species.

Mir Misbahuddin, is Professor of Pharmacology in the Faculty of Basic Science and Paraclinical Science, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. He received his MBBS (1979) from the Mymensingh Medical College under The University of Dhaka, and PhD (1988) from The University of Tokushima School of Medicine, Tokushima, Japan. He joined as Associate Professor at the Institute of Postgraduate Medicine and Research, Dhaka in 1993 and was promoted to Professor in Bangabandhu Sheikh Mujib Medical University in 2001. His research interest is to find out the drug for the treatment of arsenicosis. In addition, he is conducting clinical trials and bioequivalence study. He is, currently, the editor of Bangladesh Journal of Pharmacology. He was the editor of Bangladesh Medical Research Council Bulletin, Bangladesh Journal of Physiology and Pharmacology, Teachers‟ Association Journal. His keen interest is in the field of both asynchronous and synchronous virtual pharmacology. In asynchronous teaching, a student can use the teaching contents from a website at anytime, from anywhere and several times. In the synchronous teacher, he is trying to arrange live lectures for students of Pharmacology at under – and post-graduate level from home and abroad. He edited six books on his subject.

About the Book:

1. Why did I Decide to Write this Book?
I considered deeply who will be the reader before deciding to write this book. When you look at the Indian history of educational system, guardian sent his child to the teacher’s house (Gurugriho) for learning. Subsequently teacher shifted his class from the house to under a tree when the number of students increased. Later on, teaching was limited to textbook and brick-based face to face teaching at classroom. At present teaching contents are available in internet.

Arsenic contamination has changed our concept of safe drinking water. We failed to motivate our people, politicians and beurocrates to understand the risk assessment process that other risks to life and livelihood are as grave as arsenic. A lot of information is available about arsenic and arsenicosis in internet. Reader has less time to read those and sometime confused which are authentic.

2. Who is the Reader?
Doctor working in the arsenic endemic area will be the reader of this book.

How I became a Toxicologist?
I joined in my present working place as Associate Professor in 1993. The research activities in our department were mainly focused on the therapeutic effects of spirulina, a blue-green algae. High concentration of arsenic in the drinking water as well as case of arsenicosis was first diagnosed in Bangladesh in 1993. Two to three years were required for official recognition of this disease by the Government of Bangladesh. In 1997, one of our MPhil students showed interest to examine the curative effect of spirulina in arsenicosis as a part of his thesis work. At that time we had no facility for the estimation of arsenic in water or urine. We, then, started to use the qualitative method (Gutzeit’s test) for the presence of arsenic. Then we conducted an open trial on a few cases of arsenicosis with spirulina, which is available in our drug store as alternative medicine. Therefore, we purchased spirulina powder and then provided to patients as a part of treatment because there was no specfic treatment of arsenicosis. Surprising results were obtained when we saw the clinical improvement after 4 months of treatment. That study was not well designed and we did not estimate the amount of arsenic in hair or nail. Only urine of the patient was examined for the presence of arsenic in order to confirm the diagnosis. Then I thought how spirulina relieved arsenicosis. I placed some spirulina powder in an ordinary syringe (5 mL) and placed vertically like a column chromatography. I poured some amount of arsenic contaminated water at the top of spirulina powder and then collected water sample in a test tube placed at the bottom. The water sample was then tested for total arsenic level. Arsenic was not found when it passed through spirulina. Then my idea was shifted from spirulina to water hyacinth. As arsenic is present in underground water in Bangladesh, but not in surface water like pond or river. Pond contains a lot of water hyacinth. Like spirulina, water hyacinth may have an important role in removing arsenic from pond’s water. I collected some water hyacinth and placed in a bucket containing arsenic contaminated water. Again I surprized to see that water hyacinth removed arsenic from water within a few hours.

When I go through the published articles on arsenic, I found that Bangladesh is severely affected by chronic poisoning with high concentration of arsenic. Most of the research works were done on epidemiology and mitigation. Only a few papers were on the treatment of arsenicosis.

Then I decided to start research to find out a drug that will be effective for the treatment of arsenicosis. I changed my laboratory setup that is gradually shifted from the Gutzeit’s method to other methods using spectrophotometer, atomic absorption spectrometer (AAS) and atomic fluorescence spectroscopy (AFS).

3. What Initiates me to Write this Book?
One day I received an email from the Science Publishing Group to wtire a book. Then I decided to write a book on arsenicosis.

4. Answers of Many Questions
I wanted to solve a number of questions that had been raised in a scientific saminar on “Arsenic: Health effects, mechanism of action and research issue” held in September, 1997 at Maryland, USA.

5. Previous Experiences
I wrote two arsenic related books. These previuos experiences helped me in writing this book.

6. Authanticity
A lot of information is given in this book. Only the future will tell what percentage of the information in this book is correct.

Prosthetic limbs may work wonders for restoring lost function in some amputees, but one thing they can’t do is restore an accurate sense of touch. Now, researchers report that one day in the not too distant future, those artificial arms and legs may have a sense of touch closely resembling the real thing. Using a two-ply of flexible, thin plastic, scientists have created novel electronic sensors that send signals to the brain tissue of mice that closely mimic the nerve messages of touch sensors in human skin.

Multiple research teams have long worked on restoring touch to people with prosthetic limbs. 2 years ago, for example, a group at Case Western Reserve University in Cleveland, Ohio, reported giving people with prosthetic hands a sense of touch by wiring pressure sensors on the hands to peripheral nerves in their arms.

Yet although these advances have restored a rudimentary sense of touch, the sensors and signals are very different from those sent by mechanoreceptors, natural touch sensors in the skin. For starters, natural mechanoreceptors put out what amounts to a digital signal. When they sense pressure, they fire a stream of nerve impulses; the more pressure, the higher the frequency of pulses. But previous tactile sensors have been analogue devices, where more pressure produces a stronger electrical signal, rather than a more frequent stream of pulses. The electrical signals must then be sent to another processing chip that converts the strength of the signals to a digital stream of pulses that is only then sent on to peripheral nerves or brain tissue.

Inspired by natural mechanoreceptors, researchers led by Zhenan Bao, a chemical engineer at Stanford University in Palo Alto, California, set out to make sensors that churn out digital signals directly. Bao’s group started by refining sensors that they first made 5 years ago. In that earlier work, the group designed tiny rubber pillars containing electrically conductive carbon nanotubes, which were placed over a pair of electrodes side by side. When no pressure is applied, the rubber, which is an insulator, prevents current from flowing between the two electrodes. But when touched, the pressure squishes the pillars, pushing the conductive nanotubes together to make a continuous electrical path and allowing current to flow. When the pressure is removed, the rubber pillars bounce back to their original shape.

For their current work, Bao and her colleagues turned their pillars into inverted pyramids and tweaked their size so they were sensitive to a range of pressures, from a light touch to a firm handshake. They also changed the electrode setup and added another layer of flexible electronic devices, known as ring oscillators, which convert the electrical signals emerging from the touch sensitive pyramids to a stream of digital electrical pulses. The upshot was that—just like the signals from natural mechanoreceptors—when more pressure is applied, the oscillators turn out pulses at a higher frequency.

But Bao’s group didn’t stop there. The Stanford team also wanted to see if brain tissues could receive these signals. That’s typically done by inserting metal electrodes into the so-called somatosensory cortex of animals and watching their response. But metal electrodes can quickly damage natural brain tissue, making it impossible to study the transfer of signals over extended periods. So for their current study, Bao’s team decided to send the electronic pulses coming from the touch sensors to a light emitting diode, which converted them into a stream of pulses of blue light. Bao’s team then partnered with Stanford colleagues, led by Karl Deisseroth, to genetically engineer somatosensory cortex tissue of mice to absorb blue light and fire in response. They sacrificed some of the engineered mice and isolated a slice of the light-sensitive somatosensory cortex, which remained viable for several hours. Finally, they tested their touch sensors and monitored whether the mouse brain tissue received the signals and fired in response. In today’s Science they report that the brain neural tissue faithfully reproduced the firing patterns coming from the touch sensor. That raises hopes that such sensors may eventually help restore a natural sense of touch to amputees, Bao says.

“It’s great to see research moving in this direction, and this particular paper is impressive,” says John Rogers, a chemist and expert in flexible electronics at the University of Illinois, Urbana-Champaign. Both Rogers and Bao note, however, that giving amputees a natural-like sense of touch still has a ways to go. Doctors, for example, won’t be able to engineer human brain tissue to receive light signals. That means researchers will need to find other ways to pass electrical signals from a prostheses to the brain in a way that is stable and safe for long periods of time. Bao says she hopes to use flexible organic electronics for this task as well. Eventually, as these different threads of research are woven together, it’s likely to give people with prosthetic limbs a whole new feel for their surroundings.